mirror of
https://github.com/moparisthebest/xeps
synced 2024-11-23 01:32:22 -05:00
195 lines
6.4 KiB
XML
195 lines
6.4 KiB
XML
<?xml version='1.0' encoding='UTF-8'?>
|
|
<!DOCTYPE xep SYSTEM 'xep.dtd' [
|
|
<!ENTITY % ents SYSTEM 'xep.ent'>
|
|
%ents;
|
|
]>
|
|
<?xml-stylesheet type='text/xsl' href='xep.xsl'?>
|
|
<xep>
|
|
<header>
|
|
<title>Pre-auth Registration Key Generation and Validation</title>
|
|
<abstract>
|
|
This specification updates XEP-0401 and XEP-0445 by specifying a shared
|
|
format for the pre-authenticated registration token.
|
|
</abstract>
|
|
&LEGALNOTICE;
|
|
<number>xxxx</number>
|
|
<status>ProtoXEP</status>
|
|
<type>Standards Track</type>
|
|
<sig>Standards</sig>
|
|
<approver>Council</approver>
|
|
<dependencies>
|
|
<spec>XMPP Core</spec>
|
|
<spec>XEP-0401</spec>
|
|
<spec>XEP-0445</spec>
|
|
</dependencies>
|
|
<supersedes/>
|
|
<supersededby/>
|
|
<shortname>preauth-token</shortname>
|
|
&sam;
|
|
<revision>
|
|
<version>0.0.1</version>
|
|
<date>2021-06-06</date>
|
|
<initials>ssw</initials>
|
|
<remark><p>First draft.</p></remark>
|
|
</revision>
|
|
</header>
|
|
<section1 topic='Introduction' anchor='intro'>
|
|
<p>
|
|
Both &xep0401; and &xep0445; specify a mechanism for requesting a token from
|
|
a server that can be exchanged for registration at a later date.
|
|
However, neither XEP defines the format of this token, or a recommended
|
|
algorithm for generating it.
|
|
This means that each server may choose a unique format and that any token
|
|
issuing entity must either only support a specific servers token format, or
|
|
must connect to the server with an admin account so that it can ask the
|
|
server for tokens.
|
|
</p>
|
|
<p>
|
|
This specification rectifies this by specifying a server-agnostic format for
|
|
pre-auth tokens and an algorithm for generating them.
|
|
This enables third-party trusted services that share a private key to
|
|
sign a token that can later be verified by the server to register a user.
|
|
</p>
|
|
</section1>
|
|
<section1 topic='Requirements' anchor='reqs'>
|
|
<ul>
|
|
<li>
|
|
Tokens issued by a third-party authorization server MUST be verifiable by
|
|
any authentication server supporting this specification.
|
|
</li>
|
|
<li>
|
|
Generated tokens MUST be URL safe.
|
|
</li>
|
|
<li>
|
|
<p>
|
|
The algorithm for generating tokens SHOULD allow verification of the
|
|
following inputs:
|
|
</p>
|
|
<ul>
|
|
<li>an optional username,</li>
|
|
<li>a list of hostnames for which the user can register,</li>
|
|
<li>and an optional expiration time.</li>
|
|
</ul>
|
|
</li>
|
|
</ul>
|
|
</section1>
|
|
<section1 topic='Glossary' anchor='glossary'>
|
|
<dl>
|
|
<di>
|
|
<dt>Authentication server</dt>
|
|
<dd>
|
|
The server authenticating the user using IBR or SASL, normally the XMPP
|
|
server.
|
|
</dd>
|
|
</di>
|
|
<di>
|
|
<dt>Authorization server</dt>
|
|
<dd>
|
|
A server issuing a token authorizing the user to register.
|
|
This may be the XMPP server, or another entity that shares its private
|
|
key.
|
|
</dd>
|
|
</di>
|
|
<di>
|
|
<dt>IBR</dt>
|
|
<dd>
|
|
In-band Registration, as defined by either &xep0077; or &xep0389;
|
|
</dd>
|
|
</di>
|
|
<di>
|
|
<dt>Key</dt>
|
|
<dd>
|
|
A shared secret that is used to sign and validate tokens.
|
|
</dd>
|
|
</di>
|
|
</dl>
|
|
</section1>
|
|
<section1 topic='Use Cases' anchor='usecases'>
|
|
<ul>
|
|
<li>
|
|
As the admin of a social media network I want to allow my users to
|
|
self-provision accounts on our instant messaging platform without
|
|
involving the XMPP admin or requiring that the provisioning service speak
|
|
with the XMPP server.
|
|
</li>
|
|
<li>
|
|
As the admin of an XMPP server I want to generate tokens that can be
|
|
redeemed for an account at a later date even though the XMPP server is
|
|
temporarily down for maintenance.
|
|
</li>
|
|
<li>
|
|
As the representative of a chat network attending a conference, I want to
|
|
be able to print invitations to sign up for an account at our server even
|
|
though the conference WiFi is spotty and I may not be able to remain
|
|
connected to the server.
|
|
Furthermore, I want to use a different private key than the one used by
|
|
user invites so that I can see how many users from the conference
|
|
registered.
|
|
</li>
|
|
</ul>
|
|
</section1>
|
|
<section1 topic='Business Rules' anchor='rules'>
|
|
<p>
|
|
The following algorithm is used to generate tokens where "," is a separator
|
|
and not part of any actual input and <tt>$key</tt> is the shared secret key.
|
|
All uses of base64 are the Raw URL encoding (with no padding characters)
|
|
defined in &rfc4648;
|
|
HMAC-SHA256 is a Keyed-Hash Message Authentication Code (see &nistfips198a;)
|
|
using the SHA256 hashing algorithm (see &nistfips180-2;).
|
|
</p>
|
|
<code>
|
|
// Current time rounded up and converted to milliseconds.
|
|
expiration = ($currentTime + 1e6 -1) / 1e6
|
|
jids = {
|
|
JID1, ':',
|
|
JID2, ':',
|
|
JID3, ':',
|
|
…
|
|
JIDFinal
|
|
}
|
|
signature = HMAC-SHA256
|
|
(
|
|
$key,
|
|
$jids, ':',
|
|
$expiration
|
|
)
|
|
token = {
|
|
base64-raw-url($signature), ':',
|
|
base64-raw-url($jids), ':',
|
|
$expiration,
|
|
}
|
|
</code>
|
|
</section1>
|
|
<section1 topic='Implementation Notes' anchor='impl'>
|
|
<p>
|
|
If the shared key is longer than the block size it will be hashed by some
|
|
HMAC implementations, otherwise it is left unhashed.
|
|
This is not represented in the algorithm above, but if it is not done the
|
|
user must determine whether the input key needs hashing themselves.
|
|
Input keys shorter than the block size are not hashed.
|
|
</p>
|
|
</section1>
|
|
<section1 topic='Security Considerations' anchor='security'>
|
|
<p>
|
|
The secret key SHOULD be at least half the length of the SHA256 output (ie.
|
|
16 bytes).
|
|
No key stretching is performed by this algorithm, so the user should take
|
|
care to pick a long key.
|
|
</p>
|
|
<p>
|
|
Creation of the secret key MUST NOT require communication between the
|
|
authentication server, the authorization server, or a third party such as a
|
|
database.
|
|
</p>
|
|
</section1>
|
|
<section1 topic='IANA Considerations' anchor='iana'>
|
|
<p>This document requires no interaction with &IANA;</p>
|
|
</section1>
|
|
<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
|
|
<p>This document requires no action from the ®ISTRAR;</p>
|
|
</section1>
|
|
<section1 topic='XML Schema' anchor='schema'>
|
|
<p>This document does not define an XML namespace requiring a schema.</p>
|
|
</section1>
|
|
</xep>
|